Catalytic conversion of ureaformaldehyde resins



Patented Feb. 24, 1942 7 CATALYTIC CONVERSION OF UREA- FORMALDEHYDE RESINS Theodore S. Hodgins, Royal Oak, and Almon'G. Hovey, Birmingham, Mich., assignors to Reich- 7 holdChemicals, 1110., Detroit, Mich. l

application September 13, a 50. Divided and this ap- No Drawing. Original 1939, Serial No; 294,7 I plication February 17, 1940, Serial No.

10 Claims. (Cl. 260-71) The invention. relates to the conversion of urea-formaldehyde and other convertible resins accelerator. The present application is a division of our application Serial No. 294,750 filed Sept. 13,1939. I I p I Urea-formaldehyde resins as coating compositions have been known essentially as polymerizing resins rather than oxidizing resins, and for such purposes, hitherto the conversion has required heat. However, there are many materials, such as paper, wood, leather, rubber, etc., which by the use of a special acidic catalyst'or latent ill do not stand the use of heat to such coating compositions on account pf drastic decomposi tion which is likely. We have found that by the introduction .of' special acidic catalysts,' these urea-formaldehyde resins, particularly those of the urea formaldehyde monohydric alcohol type which are so successfully used for coatingsanjd which are of the'type disclosed in our companion applications Serial Nos. 203,149, filedJipril 20, 1938 ,now issued-asjU.' S Batent No. 2,221,708;

,duces marked instability of clear, transparent, glossy, hard, glass-like fin- I ish'es which may be applied on paper, 'wood,

leather, artificial leather, rubber, and other materials. On wood, the finishes may be ready for sanding within 4 hours if necessary, the films being as hard as lacquer and yet very much more fire-resistant. The use of these catalysts, therefore, opens up fields for air-drying urea-formaldehyderesins', for dimethylol-urea-acetal resins, for urea-formaldehyde-monohydric alcohol resins, for urea-phenol formaldehyde resins, etc., which have never before been anticipated.

Weare aware of the use of acidic catalysts or those of an inorganic nature such as zinc chloride, hydrochloric acid, sulphuric acid, nitric acid, aluminum chloride, iron chloride, and the like. The use of such catalysts, however, prov I the product upon storage. Stability of the vehicle is the prime necessity for the use not only of these accelerators in air-drying shelf goods, but is also a very desirable characteristic for industrial work.

234,022 filed October '8, 1938,1nowissued as, U. S.

Patent No. 2,168,477, dated August 8, 1939; 147,- 568 filed June 10, l9 37,' now issued as U. S. Patent No. 2,109,291 datedFebruary22, 1938; 237,- 578 filed'October 28, 1938, now issued as U. S. Patent No. 2,226,518j' 239,878 filed November 10, 1938, now issued as U. S. Patent No. 2,187,081; 247,988 filed December 27, 1938, now issued as U. S. Patent No. 2,261,084; 268,782 filed April 19, 1939, now issued as U. .5. Patent No. 2,222,506; 270,864 filed April 29, 1939, now issued as U. S. Patent No. 2,215,038; 280,388 filed-June 21, 1939, nowissued as-U. S. Patent No. 2,233,320; and 286,729 filed July 26, 1939, now issued as U. S.

Patent No. 2,227,223, may be converted in a relv atively short time at substantially room temperature. In all these applications, urea-formaldehyde resins are described which can use catalysts of the type which we are about to describe for'greater usefulness without the application of heat or, at least, with a very low bake as compared to the extremely high bake which has been hithertofore necessary for complete conversion. formaldehyde resins, those which are prepared from dimethylolurea and acetals of monohydric alcohols are also very much improved by the use ,of these catalysts in lowering the baking temperature or in air-drying. work.

The advantages of the use of these catalysts.

Films which would reare readily apparent. main as tacky as flypaper and which are still poor inwater-reslstance may be converted to Besides .urea

in converting the films Serial No. 203,148

There is nothing so stability because one never knows the life of the product.

This 'question of lack of stability is a stumbling block on many commercial applications. As a typical example of this, we quote from the patent of Battye, Marsh, Tankard, Watson, and Wood, U. S. Patent 2,088,227 (July 27, .1937) page 1, line 50 to commercial possibilities is rendered relatively useless by the fact that it is stable only for about 5 hours at-15-16? C.

In our U. S. application Serial No. 234,022, filed October 8, 1938, and issued as U. S. Patent 2,168,477, dated August 8, 1939, we have distion product. The use of this phosphoric acid catalyst constituted a great improvement over filed April 20, 1938, now-Patent No. 2,185,167 dated Dec. 26, 1939, because with this catalyst we obtained a better conversion in 5 minutes at F. than we did in 5 minutes at 250 F. without it. Our present invention however, constitutes a still further improvement over this disclosure in Serial No. 234,022 now Patent No. 2,168,477 dated Aug. 8, 1939. Our new catalysts are partly organic and partly inorganic, the inorganic portion consisting of radical-s obtained fromthe use of phosphoric anhydisagreeable as treacherous the bottom of the page, and page 2, lines 1-20 inclusive. In Example 1 of that, 'patent a urea-formaldehyde solution of great hydroxy compounds.

polyhydric alcohols which have incidental watersolubillty. Catalysts may be preparedin a similar way which are admirable foruse in the so-called solvent type of urea-formaldehyde resins, i. e., resins such as those described in our Serial Nos. 239,878; 268,782 and 286,729 of which a ureaformaldehyde-butanol condensation product is atypical example. Catalysts hich may be used with the solventtype are, forl example, those derived from (mono or di) p osphoricesters of fatty alcohols or of castor oil, which are complex monohydric alcohol-like bodies. It will thus be seen that these catalysts are generic to the basic reactionof P2O5+ROH, the nature of the alcohol determining the nature of the catalyst, and influences the operativeness of the resulting catalyst for the type of resin in which it is to be used, 1. e.,, whether hydrophobic or hydrophillic in nature.

Our process, the preparation of acidic catalysts,'is not to be confused with the preparation of neutral esters of phosphoric acid, for example Bannister's U. S, Patent 1,799,349 issued April 7, 1931, that is, trialkyl phosphate. We are invent type urea-formaldehyde resins are prepared by reacting phosphoric anhydride in such proportions as to form the monoand/or diesters with alcohols of carbon atom chain length of 3 or greater, such as propyl, butyl, amyl, octyl alcohol, lauryl alcohol, and others in the series. Other substances which have free hydroxyl groups andwhich may be considered as being eifectively complex alcohols may be employed. Among these are: castor oil which has one free hydroxyl group per each fatty acid radical or three hydroxyl groups per mol of oil, also the monoalkyl ethers of ethylene glycol and of other polyhydric alcohols. The complex polyhydric alcohol-like body which was described in our Serial No. 147,568 (now U. S. Patent 2,109,291) may also be reacted with P205 to form a complex accelerator.

As specific examples of our invention, we. quote the following:

Example 1 14.3 gramsof P205 is wet with 10, grams of mineral spirits (boiling range 300-400 F.) and 10 grams of butyl cellosolve (the monobutyl ether of ethylene glycol). The catalyst is prepared by slowly. adding the P205 which previously has is to result. The process is carried out'in a terested only in the monoor dialkyl phosphates,

i. e. those hich have capacity for liberating hydrogen-i n's. Furthermore, it does not have to be a pure compound, that is, neither: the monoor di-,' but may be a mixture of them and still be "very'eflective. Even slight amounts of trialkyl 40 (completely saturated) phosphate may not be detrimental. The formation of the accelerators may be described by the general reaction:

For catalyzing the water-soluble urea-formaldehyde type, monoand di-phosphoric esters and/or their mixtures of the following alcohols may be employed:- glycerol, ethylene glycol, propylene glycol, butylene glycol, sorbitol, mannitol, trimethylene glycol, dextrose and other poly- Starch and even cellulose may alsov be used as catalytic material when esterified to a partial extent with phosphoric anhydride. Short, straight chain alcohols, such as methyl alcoholand ethyl alcohol, are capable of forming water-soluble mono: and di-phosphates which are useful in the water-soluble type when they are not completely esterifled. When they are completely neutralized, of course, their catalytic effect is practically nil and their action becomes that of a water-soluble plasticizer which is really the reverse of the action of our accelerators.

Catalysts which are very efiective for the solstainless steel doughmixer of the Werner and Pfleiderer type and usually requires 6-8 hours to give a product 83.4% non-volatile. The product is highly viscous, and therefore, the product cannot be prepared by ordinary agitation; it re- 1 quires equipment strong enough to turn a very viscous material, having an absolute viscosity approaching 200 poises at 25 C. in the final stages. On account of the high viscosity, it is generally reduced to non-volatile with solvent, butanol, anhydrous alcohol, monobutyl ether of ethylene glycol, aromatic hydrocarbons and aliphatic hydrocarbons. This particular product, when thinned to 50.0% non-volatile,

5 can be identified by a P205 content of 7.15% by weight. The viscosity at 50% non-volatile in denatured alcohol is of the order of 4-5 poises at 25 C. and resembles a light-colored resinous product in appearance or a light sticky syrup.

540 grams of the above accelerator added to 100 grams of a urea-formaldehyde-butanol condensation product (60% solution in butanol) will produce an air-drying urea-formaldehyde resin film which will air-dry in 2-4 hours ready to sand. Without this accelerator, the same ureaiormaldehyde solution applied under the same conditions takes 2-3 days to air-dry.

The stability of the urea-formaldehyde resin solution containing the accelerator is 3-6 months at room temperature in contrast to the same resin to which an addition of an inorganic acid catalyst dissolved in alcohol,.such HCl, is stable for only a few hours.

Example 2 I Grams Mineral spirits 270 Butyl alcohol (normal) 170 Anhydrous alcohol .Yield=4,179 grams at 65.0% non-volatile of a very light straw colored, sticky, viscous liquid with a viscosity of approximately 10 poises.

- parts of the above catalyst'added to 120 parts by weight of a urea-formaldehyde-butanol condensation product (60% non-volatile in an equal mixture of butanol and anhydrous alcohol) makes a very satisfactory air-drying urea resin finish which dries in 1 -2' hours to a tack free, firm condition and can be sanded in'3-4 hours. These films were cast at .003 of an inch and al-. lowed to dry at approximately 25 C. Without the catalyst, the drying time was 2-3 days. The

stability of this catalyzed urea-formaldehyde resin was between 3 and 6 months as extreme, averaging 5 months at room temperature storage as compared to a matter of only a few hours if an inorganic catalystsuch IiCl was added in alcoholic medium.

Example 3 An accelerator was prepared by wetting 3280 grams of P205 with 300 grams of mineral spirits and300 grams of cello-solve (as in Example 1) and then reacting with 3300 grams of octyl alcohol over a period of 6-8 'hours at -50. C. in a Werner and Pileiderer doughmixer made of stainless steel. This accelerator was thinned for 4 months on room temperature storage,

whereas, the same solution, catalyzed to the same drying rate by an inorganic accelerator such as HCl dissolvedin alcohol, had astability limited to that of a few hours.

Example 4 I 2000 grams of P205 were wet with .2500 grams of toluol and added to a mixture consisting of Diolin (1,9 octadecanediol), 2000 grams; toluol, 2500 grams; butanol, 1400 grams. The reaction takes place in a Werner and Pfleiderer stainless steel doughmixer in. 6-8 hours at 2550 C. as in Example 1. Toward the end of the reaction, this product is a very thick mass, stirring with difliculty in the doughmixer and having a viscosity of about 200 poises at 25 C. The material was thinned to non-volatilewith the addition of 600 grams more of butanol and 1000 grams of end of this period, a mixture of 4.58 grams of ortho-phosphoric acid and an equal amount of water are added. The mixture is then distilled for 4 hours 'at 65 C. or until'350 grams of distillate (water) are removed. At this stage,

500 grams of anhydrous alcohol mixed with 4.6

grams of 75% ortho-phosphoric acid are added and the who e batch stirred. The yield is 908 grams.

To 100 grams of the above resin solution are added 5-6 grams of the catalyst described in this example. A very stable catalyzed solution results and the films, while not so transparent and water-white as those of the straight urea-formaldehyde resins containing no phenol, are nevertheless, very desirable because they air-dry very hard in 1 hour, and in the film thickness in which they are applied, they appear to be practically water-white. They can can sanded in 2 hours and a second finish then applied if necessary.

Example 5 v 3280 grams of P205 are wet with 400 grams of butanol and added to 2760 grams of ethylene glycol and reacted as in Example 1. In this case, however, the resulting product is watersoluble and when thinned down to 50% non volatile with water, has a rather low viscosity (not greater than -2 poises) and is water-white and admirable for use with water-soluble, waterwhite, heat-convertible resinous products such as the urea-formaldehyde-ethyleneglycol products, I

.in water; thus producing very stable solutions which are much better on stability than those f described in U. S. Patent 2,168,477 which use anhydrous ethyl alcohol. The result is a medium viscosity liquid of approximately 4-6 poises which is miscible with a urea-formaldehyde-butanol resin and similar resins.

This catalyst is'especially adaptable to ureaphenol-formaldehyde resins such as the follow- Grams Bis-phenol 40 Aqueous 37% formaldehyde 140 Potassium hydroxide 4 Water 4 only phosphoric acid as a catalyst. The films cast on the resin solutions using. this catalyst can be rapidly air-dried in less than 1 hour and baked inthin films in a shorter time at 30 seconds at 300 F. on light weight cloth, paper andthe like, said films being water-white and very resistant to discoloration, on either air-drying or baking, the grease-resistance also being a very desirable characteristic. Fields in which watersoluble resins of this type are of value are in rected particularly to the preparation of coatingcompositions, the invention in its broadest aspects contemplates the use of the new catalysts in preparation of resins to be employed in molding and laminating work in which field rapid speed of conversion is of utmost importance.

We claim:

1. A process for converting an id convertible urea-formaldehyde resin whic adding to the resin a preformed accelerator, comprising an acid alkyl phosphate containing solely phosphoric and alkyl radicals, wherein 'the alkyl -radical has a carbon chain length of It least 3.

comprises 2. A process for converting an acid convertible urea-formaldehyde resin which comprises adding to the resin a preformed accelerator comprising a mixture of monoand dialkyl phosphate containing solely phosphoric and alkyl radicals, wherein the alkyl radical has a carbon chain length of at least 3.

3. A process for converting an acid convertible urea-formaldehyde resin, which comprises adding to the resin a preformed accelerator comprising an acid ester containing solely phosphoric and hydrocarbon radicals.

4. A process as set forth in claim 3 wherein the accelerator is added to a cold resin.

5. A process as set forth in claim 3 wherein the resin to be treated is dissolved in an organic solvent.

6. A process as set forth in claim 3 wherein the resin treated is a urea-formaldehyde-monohydrlc alcohol resin.

7. A process as set forth in claim 3 wherein the resin treated is a urea-formaldehydebutanol condensation product.

8. A composition comprising a cold acid setting urea-formaldehyde resin and a preformed accelerator comprising an acid ester containing solely phosphoric and hydrocarbon radicals.

9. A coating composition comprising a cold solution of an acid setting urea-formaldehyde resin'in an organic solvent, and a preformed 

